Process for making inactive menthol



Patented Sept. 23, 1930 136mm;STA ES.

xanniso'rronnkorn, on nnssetnoan-onnaxassnn, AND ARTHUR sER'mI, or DrIssEt nomarrnnnnr, GERMANY, ASSIGNORS r0 ai-itnmrscnn KeMP ER-F RIK ansr tt' SGHAIE'T MIT BEsoHRANKrnR HAIETUNG, or DUSSELDORF--OBEBKASSEL, GERMANY raoonss non MAKING inncrrvn MENTHOL PATENT oFFlceIj f No Drawing. Original application filed June 30, 1927, Serial No. 202,739, and in Germany February 15, i

1927. Divided and this application filed -This is a process for the productionof inactive menthol, new isomer of inactive men-. thol and'making thesame, being a divisional application of application Serial No. 202,-. 739 filed J1me 30th, 1927. r 1

This process for the production of inactive menthol, the racemate of natural menthol consists in subjecting inactive neo-isomenthol (melting point 1244:") acid-phthalate melting point -92 C. to hydrogenating catalysts with heat in the presence of hydrogen with 01"without pressure, so that an. isomerization results and treating the menthols mixturewith refrigeration, or fractional distillation, so that fixed inactive menthol is obtained which is purified by crystallizing the esters or acid esters.

It is possible toisornerize inactive neo-isomenthol alone or in mixtures with other substances as for instance with inactive isomenthol having a melting point of 53 C. Gatalyzers suggested for hydrogenation as well as isomerization according to the process herein described is nickel, cobalt, copper, platinum, palladium or mixtures of these in powdered form or used with carriers such as kieselguhr, asbestos, pumice stone, bariumsulphate and similar materials. Instead of metals, the oxygen compounds can be used or the carbonaceous compounds such as carbonates and formiates which are .easily olecomposed.

The crude inactive menthol which is obtained according to this described process can be purified e. g. it can be transformed into esters such as ester of paranitrobenzoic acid, carbonate, borate, acidphthalate or -succinate, these being recrystallized and then saponified as pure esters or acid esters as described in the U. S. Patent No. 1,672,3 l6.

Example kilograms of inactive neo-isomenthol are treated with 2 kilograms of a nickel and copper catalyst under a pressure of about 10 atmospheres of hydrogen at'a temperature of C. with agitation until an equilibrium of transformation that is to say until a maximum yield of inactive menthol is ob.- tained which usually takes about 24 hours.

September 20, 1928. Serial-No. 307,333.

From the mixture of isomers the crude inactive menthol is obtained through recrystallization or fractional distillation or by a combination' of both methods and further purified by transformation into the crystallized esters. In this way pure inactive menthol of a melting point 84l36 C. is obtained.

The isomers of the inactive menthol which are obtained in this process of separation and purification can be again treated, eventually with the addition of freshinactive neoisomenthol.

We claim r 1. The process 1"or manufacturinginactive menthol, the racemate of natural menthol, which consists in heating inactive neo-iso menthol with hydrogenating catalysts and hydrogen under pressure and agitation and separating from the reaction product the ob tained crude inactive menthol. 2. The process for manufacturinginactive menthol, the racemate of natural menthol,

which consists in heating inactive 'neo-iso-' menthol admixed with. materials which are capable of being hydrogenated to inactive menthols mixtures with hydrogenating catalysts and hydrogen under pressure-and agitation and separating from the reaction prodnot the obtained crude'inactive menthol.

3. The process for manufacturing inac-.

tive menthol, the racemate of natural menthol, wh ch consists in heatlng inactive neoisomenthol admixed with other isomers of inmenthol with hydrogenating catalysts ai'id hydrogen ,under agitation, and separating from the reaction product crude-inactive.

a r s 95 5. The process ior manufacturlnginactive menthol.

menthol, the racemate of natural menthol,

which consists in heating inactive neo-isomenthol, with hydrogenating catalystsand hydrogen under agitation and separat ng:

from-the reaction product crude inactive menthol by physical methods.

6. The process for manufacturing inactive menthol, the racemate of natural menthol, which consists in heating. inactive neoiso-. menthol with hydrogenating catalysts and hydrogen under agitation and separating from'the reaction product crude inactive menthol by fractional distillation. I

7. The process for manufacturing inactive menthol, the racemate of natural menthol, which consists in heating inactive nee-isomenthol with hydrogenating catalysts and hydrogen under pressure and agitation and separating from the reaction product the obtained crude inactive menthol by physical methods.

8. The process for manufacturing inactive menthol, the racemate of natural menthol, whichconsists in heating inactive 'neo-isomenthol with hydrogenating catalysts and hydrogen under pressure and agitation and separating from the reaction product the obtained crude inactive menthol by fractional distillation.

9. The process for manufacturing inactive menthol, the raccmate of natural menthol,

which consists in heating inactive neo-isomenthol, mixed wlth materials which are capable of being hydrogenated to inactive menthol mixtures, with hydrogenatnig catalysts and hydrogen under pressure and agitation and separating from the reaction product crude inactive menthol by physical methods.

10. The process for manufacturing inactive menthol, the racemate'of natural menthol, which consists in. heating inactive neoisomenthol, mixed with materials which are capable of being hydrogenated to inactive menthol mixtures, with hydrogenating catalysts and hydrogen under pressure and agitation and separating from the reaction product crude inactive menthol-byfractional distillation.

11. The process for manufacturinginactive menthol, the racemateof natural men-- thol, which consists in heating inactive neoisomenthol mixed with other isomers of in active menthol with hydrogenating catalysts and hy'drogenunder agitation and separating from the reaction product crude inactive menthol by physical methods.

12. The process for manufacturing inactive menthol, the racemate of natural menthol, which c-onsists in heating inactive n'eo isomenthol' m xed w1th other isomers-of 111 hydrogen under agitation and separating from the reaction product crude inactive menthol b fractional crystallization.

14. he process for manufacturing inactive menthol, the racemate of-natural menthol, which consists in heating inactive neoisomenthol with hydrogenating catalysts and hydrogen under pressure and agitation and separating from the reaction product-the-ob-- tained crude inactive menthol by" fractional crystallization.

15. The process for manufacturing inactive menthol, the racemate of natural menthol, which consists in heati-nginactiye neoisomenthol mixed with materials which are capable of being hydrogenated to inactive menthol mixtures with hydrogenatingjcatalysts and hydrogen under pressure and agitation and separating from the'reaction prodwhereof we afiix oursigna 

